Computer systems, such as servers, can be expanded by expansion cards but an internal space of a server is limited. In order to meet heat dissipating demands, heat dissipating devices perform the critical function of removing heat from a computer system. For example, a heat sink is provided to efficiently dissipate heat generated by a CPU, and an air guiding duct is provided to direct air out of the computer system. Due to the functional requirements, air ducts are often in the middle of the server, fans are located in an lower portion of the server, while expansion cards, cables, and other components are in the upper portions of the server. Thus, the expansion cards, cables, and other components need to be removed during the maintenance of the fans. An air guiding duct and electronic devices using the air guiding duct that can provide easy maintenance of fans would be needed.